Cash Flow Information - Schedule of Supplemental Cash Flow Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Cash paid for interest	$ 157	$ 125	$ 90
Cash paid for taxes	10	10	10
Non-cash activities:
Issuance of general partnership interests through partnership loans in current year	164	170	142
Repayment of partnership loans through distributions from partnership capital in current year	136	135	111
Declared distributions for retired partnership capital in current year but unpaid at year end	$ 113	$ 97	$ 0